The goal of Project I is to relate dynamic neuronal network properties to the intrinsic electrical activity of their constitutive neurons. The project will address three areas: A) The voltage-dependent ionic currents in in vitro Purkinje cells and their role in neuronal integration. These will be studied at macroscopic and single-channel current level using whole-cell and cell-attached patch clamp techniques and will concern INa(P) and ICa. The study will correlate in addition ionic currents to the molecular biological characteristics of the channels involved, with the ultimate aim at gene knockout and at calcium-concentration imaging to address the issue of "complex calcium microdomains." This part of the work will be done in collaboration with Dr. Hillman. A mathematical model of Purkinje cell activity will serve as a heuristic tool to assess single channel and macroscopic current results and issues concerning calcium pump and IP3 activity as determined by the imaging results. B) Functional organization of the cerebellar brain stem and its relation to motor control. Experiments performed at the single-cell level in the in vitro inferior olive slice will determine, electrophysiologically and by means of calcium imaging, the ionic basis and channel distribution responsible for neuronal oscillation. Inferior olive oscillation will be related to the regulation of electrical coupling by cerebellar nuclear return inhibition, and to an in vivo paradigm concerning the generation of movement in the vibrissal system. The study will entail multiple Purkinje cell recording and their temporal relation to spontaneous and cortically evoked vibrissal movement. The paradigm will relate ionic currents and their pharmacological properties to movement execution as modulated by the olivocerebellar system. C) The ionic basis for 40-Hz oscillation and neuropeptide modulation of calcium oscillation in single thalamic neurons and its relation to thalamothalamic and thalamocortical re-entrant oscillation and function. The studies will include multiple electrode recordings at the thalamic and cortical levels, in the isolated guinea pig brain in vitro. The experiments will be complemented by computer modeling as a predictor of network properties.